But users will not notice much of a change when the new privacy policy takes effect on March 1, experts say, noting that the update is, in part, codifying practices that have long been routine.

“Users are not likely to see any difference actually because most of what Google is doing they have been always able to do,” said Jules Polonetsky, director of the think tank Future of Privacy Forum. “They were already tracking, personalizing, and tailoring profiles for users based on the different things that you did. There now will be some more data that will be available to do this.”

The new privacy policy does not allow Google to collect more information about its users, though it does allow Google to do more with the information it has already been collecting across its services. Specifically, the terms permit Google to merge data it has compiled about its users as they engage with Google products, as well as build more comprehensive portraits by drawing on data from a greater number of Google services. YouTube, Gmail, Blogger, Google TV, Google+ and Web History, which records all searches performed on Google.com, will now be able to communicate with each other about a user’s preferences and practices. Some Google products will still maintain standalone privacy policies, such as Google Books, Chrome and Google Wallet.

Merging information gleaned across multiple services isn’t anything new for Google. A Google spokesman noted, “Privacy policies for a long time now have allowed us to combine information that’s associated with a particular Google account.”

But the policy being introduced Thursday will help Google develop richer profiles of its users, cobbled together from data about what videos they’ve watched on YouTube, what their Gmail emails say, what searches they perform and which topics they follow on Google+. Rather than keeping information about your Gmail usage separate from specifics on what you write about on Blogger, Google will pull all of those details together. All Google users will also be required to submit to the new terms, a fact that has privacy advocates up in arms.

Though Google has cast the changes as a benefit to users, saying they will enjoy a "beautifully simple" experience, the ability to piece together more information about users’ activities online will ultimately prove a boon to Google as it challenges other web companies, such as Facebook, in a war over advertising dollars and users’ time.

With more granular data about peoples’ interests, Google can better fine-tune its targeted advertising and gain an edge over its rivals by helping companies access potential customers. Gmail ads have always been tailored to the content of a user’s emails, so a user might have seen information about hotels next to an email exchange about traveling to Mexico. Following the revamped privacy policy, the ads that appear on Gmail could be tailored to a user’s search history, with queries for “sneakers” or “business cards” on Google.com yielding promotions for footwear and office gear alongside a user’s Gmail inbox.

“The privacy changes are taking place in the midst of a data arms race between Facebook, Google and other companies in the space,” said Alan Simpson, vice president of policy for Common Sense Media, an advocacy group for Internet safety issues. “They’re all working to gather as much data and personal information as they can and figuring out ways that they will use our data to develop a better advertising market.”

In addition to more targeted ads, Google users are also likely to find the web company’s products more personalized to match their interests, browsing habits and social networks. Before the privacy policy change, a user’s experience on Gmail or Google’s search engine would be unaffected by his or her choice of YouTube videos, and vice versa. After March 1, if Google sees that a user has searched for “French twist instructions,” YouTube could display videos about styling hair the next time the user visits the site.

Google noted in a video introducing the privacy changes that by sharing more information across its products, the company could deliver “more accurate spelling suggestions because you’ve typed a word before” or “tell you when you’ll be late for a meeting based on your location, calendar and local traffic conditions.”

“The companies in this space all talk in terms of the potential positive, and there are quite a few potential positives,” Simpson said. “There might well be innovations that come out of this that improve Google search, but what we don’t know is how this will impact the way data is being used. “

Google has come under fire for its failure to allow users to opt out of its privacy policy change: The terms will go into effect for all Google users come Thursday, whether they’re comfortable with the changes or not. To dodge the new policy, people can use Google products without logging into the services, or create distinct Google accounts for each Google product, though advocates argue these options are insufficient. Users can also minimize the data Google stores about them by erasing their browsing history and blocking Google from collecting information about their search queries.

Privacy experts also fear that the new policy could encourage Google rivals, which are likewise hungry for users’ personal information, to take an even more aggressive stance toward the collection of personal details and continue chipping away at people’s privacy online.

“Companies keep saying ‘this is the standard’ because they all keep moving the goal post, and every time they move the goal post, everyone jumps up and does the same thing,” said Chet Wisniewski, a security adviser at Sophos. “At some point, you’ve gone too far.”